"If I had a fostex, I might stretch it to 5 K. But in my experience, the highs get muddied if you ask the same driver to do all the work, as well as the lows of course."

I have two Fostex systems.

The FE-164 ML TQWT does a good job over the whole frequency range and only really falls a little short on loud bass passages. But it is only a 6" driver so I can forgive that weakness.

The FE-208 Sigma does much better in the bass but maybe runs out of steam at the very top. I have thought about a super-tweeter but have never tried one. I would say this driver is marginal at the very top.

Most of the Fostex systems I have heard do a good job of being truely full range. Maybe a little help at the very extremes is warrented for some recordings, but even without help the speakers sound very good all by themselves.

"In my opinion at present, single driver speakers are best used as wide band drivers, covering 5-6 of the 10 octaves. Usually from 80 Hz up to about 2500 to 5000 HZ."

I have not really felt the need to add a tweeter at the top for my Lowthers.

The bigger magnet models do a very good job of the mids and highs, they could use a little help at the bottom. I am hoping my back loaded horn design will solve the bottom without going to a multi-driver set-up.

The smaller magnet Lowthers have more bass punch but at the exxpense of a little high end. In both cases I can easily live with the Lowthers running full range with the type of music I enjoy.

Part of the challenge is to squeeze everything out of one driver. So it is a technical enclosure design issue as well as a can I enjoy the music issue.

"Of course this will depend on the drivers."

Absolutely true!

Martin

• Quarter Wavelength Loudspeaker Design